With increasing development of electronic industries, electrical devices are developed toward high integration level and high power density. As known, the high power-density design usually results in high frequency characteristics. Especially, the high frequency characteristics of magnetic elements are more critical.
FIG. 1 is a schematic perspective view illustrating the layout structure of a conventional power supply unit. As shown in FIG. 1, the conventional power supply unit 1 comprises a transformer 11, a rectifier 12 and a current transformer (CT) 13. The transformer 11, the rectifier 12 and the current transformer 13 are mounted on a system board 10. The primary winding coil of the transformer 11 receives an input voltage. The secondary winding coil of the transformer 11 is electrically connected to the system board 10 through a plurality of pins 111. The current transformer 13 comprises a conductive wire 131, which runs through the current transformer 13. The transformer 11 is electrically connected to the conductive wire 131 of the current transformer 13 through the pins 111 and the traces (not shown) of the system board 10. As such, the current outputted from the transformer 11 could be sensed by the current transformer 13. Similarly, the transformer 11 is electrically connected to the rectifier 12 through the pins 111 and the traces of the system board 10. The voltage outputted from the transformer 11 is regulated and rectified by the rectifier 12, and thus an output voltage is generated to a load (not shown).
Since the pins 111 of the transformer 11 need to be welded on the system board 10 and the transformer 11 is electrically connected to the rectifier 12 through the pins 111 and the traces of the system board 10, the distance between the secondary winding coil of the transformer 11 and the rectifier 12 is very long and the current path is also long. Under this circumstance, high power loss occurs at the welded sections and the current path. Furthermore, since the current transformer 13 of the conventional power supply unit 1 usually generates increased leakage inductance, additional power loss occurs. Under this circumstance, the reliability and the efficiency of the conventional power supply unit 1 are deteriorated. Since the transformer 11, the rectifier 12 and the current transformer 13 are electrically with each other after they are mounted on the system board 10, the process of assembling the conventional power supply unit 1 is complicated.
Therefore, there is a need of providing a power module and a circuit board assembly thereof so as to obviate the drawbacks encountered from the prior art.